Once upon a time, desktops were the tops of actual desks, and nearly all of them had a paper dictionary on or near them. The best dictionaries were so huge they needed their own stands. You can still see them in libraries. But nearly everyone who has a computer uses a Web-based dictionary, such as the cleverly named Dictionary.com, or some kind of software-based reference. TheSage's English Dictionary and Thesaurus is the latter sort. It's a free utility that maintains a huge dictionary and thesaurus locally, not online, so it's completely portable, though it can access the Internet for definitions, updates, and other needs. In fact, it will look up words in most major word processors, browsers, and e-mail clients, including Microsoft Word, Internet Explorer, and Outlook, and Mozilla's Firefox and Thunderbird. It has powerful searching, cross-referencing, and indexing features, too.
TheSage downloads at 8.52MB; about average for today and fairly tidy, considering that, with more than 200,000 definitions, 50,000 usages, and 70,000 phonetic transcriptions in the dictionary and nearly 1,400,000 word associations in the thesaurus, it would definitely be in library-stand territory, if it were printed on paper. But there's really no way for a paper dictionary to do a fraction of the things TheSage does. For instance, there's an encyclopedia of historical, geographical, political, and biomedical information.
Not long ago, a reference library as extensive as TheSage's English Dictionary and Thesaurus would have cost hundreds of dollars and taken up feet of shelf space. Today it's all free and a click away.